Structured Data and Reusable Code: UDTs and Add-On Instructions

Tag-based addressing is the reason Logix exists, and most programs never use it properly. This course is about the two features that separate a program you can extend from one you rewrite: User-Defined Data Types and Add-On Instructions.

You build a UDT that describes one real piece of equipment, put it in an array, index into it, and watch a hundred rungs collapse into a loop. Then you take working ladder and turn it into an AOI (parameters, local tags, revision notes) and instantiate it several times over real I/O.

The last module puts both together as a reusable machine object, so changing how every motor on a line behaves becomes one edit to one definition.

1. 1

   Data types, arrays and structures

   BOOL through REAL and when each is the right choice, arrays, the predefined structures behind timers and counters, and what a structure costs you.

   Available now 7 slides ~60 min 60 min lab
2. 2

   Designing a User-Defined Data Type

   Build a UDT that describes one real thing, nest it, use it as a tag, and see why a well-chosen UDT removes more code than any instruction does.

   Available now 7 slides ~60 min 60 min lab
3. 3

   Arrays of UDTs and indirect addressing

   Index into an array with a tag, loop over it, copy blocks with COP and CPS, and avoid the addressing mistakes that only show up at run time.

   Available now 7 slides ~60 min 60 min lab
4. 4

   Your first Add-On Instruction

   What an AOI is and is not, building one from working ladder, the EnableIn and EnableOut pattern, and testing it before it goes anywhere near a machine.

   Available now 7 slides ~60 min 60 min lab
5. 5

   AOI parameters, local tags and revisions

   Input, Output and InOut parameters and which to reach for, local tags, revision notes, and what source protection does to the next person who opens it.

   Available now 7 slides ~60 min 60 min lab
6. 6

   A reusable machine object

   Build a motor or valve object as a UDT plus an AOI, instantiate it several times over real I/O, and change all of them at once by editing one definition.

   Available now 7 slides ~60 min 60 min lab

Lab times are approximate: they are a guide to how long the hands-on part usually takes, not a limit. You can ask for more lab time whenever you need it.